As patients live longer and are diagnosed with chronic and often debilitating ailments, the result will be an increase in the need to place protein therapeutics, small-molecule drugs, and other medications into targeted areas throughout the body that are currently inaccessible or inconvenient as sites of administration. For example, many vision-threatening diseases, including retinitis pigmentosa, age-related macular degeneration (AMD), diabetic retinopathy, and glaucoma, are incurable and difficult to treat with currently available therapies: oral medications have systemic side effects; topical applications may sting and engender poor compliance; injections require a medical visit, can be painful, and risk infection; and sustained-release implants must typically be removed after their supply is exhausted and, moreover, offer only limited ability to change the dose in response to the clinical situation. Another example is cancer, such as breast cancer or meningiomas, where large doses of highly toxic chemotherapies such as rapamycin or irinotecan (CPT-11) are administered to the patient intravenously, resulting in numerous undesired side effects outside the targeted area.
Implantable drug-delivery systems, which may have a refillable drug reservoir, cannula, and check valve, etc., allow for controlled delivery of pharmaceutical solutions to a specified target. This approach can minimize the surgical incision needed for implantation, and avoids future or repeated invasive surgery or procedures. The implantable drug-delivery systems may, in principle, be turned on and off manually, e.g., by pressing a toggle switch, as used, for example, in pumps used for insulin therapy or intrathecal injections. However, in some applications, the pumps are too small, or too inaccessible after implantation, to allow for manual activation; for example, refillable ocular drug pumps, which usually hold <500 μL, cannot practically be accessed directly post-implantation into the eye, requiring, instead, a remote control to turn the pump on or off. Furthermore, certain drug regimens require complicated drug-delivery protocols, which may change over time depending on patient response. In these circumstances, remote operation of the drug pumps and/or execution of drug delivery protocols can reduce visits to a clinician, the risk of non-compliance, and errors in dosage events caused by self-administration.
Accordingly, various implantable drug-delivery pumps incorporate telemetry capability to facilitate communication with an external monitoring and/or control device. Such implantable pumps may be activated or deactivated remotely; their operating parameters may be non-invasively adjusted; and diagnostic data may be read out from the implantable pumps by the external monitoring device through signals transmitted and received by the telemetry circuitry. During a scheduled visit, a physician may place the monitoring and/or control device near the implantable pump and/or send signals to the implantable pump. The implant, in turn, adjusts the pump parameters and may transmit a response to the monitoring device. Typically, the telemetry circuitry comprises a coil antenna that transmits and receives signals using electromagnetic waves. A number of parameters and effects affecting the efficiency of the coil antenna, e.g., the resonant frequency, gain, quality factor (Q factor), and the thermal effect (Joule effect or heat), typically need to be considered when selecting or designing the coil antenna.
Traditionally, coil antennas incorporated in a medical telemetry systems are hand-wound, utilizing inner and/or outer dimensions as a guide without a set pattern. These coil antennas have variable characteristic parameters and, thus, do not provide optimal efficiency. In addition, the variability among antennas in production—e.g., variations in the resonant frequencies—can create problems when communicating with the external device. For example, the individual implantable devices paired with different telemetry coils may need to be programmed separately to facilitate communication with the external device. Furthermore, loosely wound coil antennas may be difficult to pack on or near the implantable device.
More sophisticated manufacturing methods, such as thin-film or thick-film deposition, etching, or electroplating may also be utilized to form the coil antennas. Antennas generated by these methods, however, are generally planar, whereas the pump devices into which they are embedded often have curved surfaces dictated by the anatomy of the implant site. As a consequence of their inability to conform to the shape of the pump device, these antennas may take up precious “real estate,” constraining the overall geometry and/or increasing the footprint of the pump device. Additionally, a coil antenna formed by, for example, film deposition, may be limited in the amount of conductive material utilized, which may not have a good Q factor and, in turn, limits its power transfer.
Consequently, there is a need for an approach to manufacturing, with accuracy, coil antennas that can be easily conformed to various geometries of drug pumps implanted in different anatomical regions.